lizrfoust wroteTechnically speaking, any RV can become fuel efficient depending on how well you take care of it. Making sure that you regularly check on the engine and the tires is one way for it to be fuel efficient. Weight is also another factor. Of course, the heavier your RV with all the stuff you have here and the things that you pack, the less efficient it is.

Just my two cents.

Well said, liz! And it's true. Looking back, we were actually burning a whole lot more fuel when we started out than now. Apparently, we were packing way too much stuff in our Motorhome so it was always be almost reaching the weight limit. It was only after when we started assessing which ones we really needed and which ones we could just leave behind. It considerably helped us lighten our motorhome.

Choosing also when you set out on your roadtrip and your route also plays a factor. Spending too much time idling while in traffic causes you to spend a lot of fuel. That's also why we usually head out at night when it's a long drive. Lesser traffic and people on the road.

Motorhomes build on the Mercedes diesel Sprinter chassis are by far the most fuel efficient, but the initial cost of those coaches is dramatically higher, which may erase a lot of the economics of higher fuel mileage. Class B and Class C coaches are both available with a Sprinter chassis. A same-size gasser Class C that sells for about $60,000 would cost about twice as much if built on the Mercedes chassis. Will your friend drive enough to save $60,000 in fuel with twice the mileage but twice the initial cost? Only your friend can answer that question. My calculations are that your break-even point is about 133,333 miles not considering the difference in maintenance costs of diesel engine vs gasoline engine, the higher cost of diesel fuel and that a Mercedes will hold its value better.

Yeah I think that is another thing to think about. Whether or not you decide to go for a diesel or gasoline engine is going to play a factor in efficiency. Also, a diesel platform will have more torque generally, which is an added bonus to the lower fuel consumption.

Fuel efficiency may be a major concern for your friend, but I think room & cost would be major concerns, Class B's may be more fuel efficient, but "generally" cost far more than a class c, I could by a LOT of fuel for the difference in cost, also "Most" Class B's are smaller and for me, more confining. And, because of their size , they are "usually" easier to maneuver and park. Not that it's not important, but If fuel efficiency is THE major concern, perhaps your friend may want to reconsider the RV life